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Does the Casimir effect prove the existence of virtual particles?
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The Casimir effect is the experimentally confirmed existence of a
force (the Casimir force) between uncharged metallic plates in vacuum.
See
http://en.wikipedia.org/wiki/Casimir_effect .
But don't trust the subsequent esoteric explanation given there!
Indeed, since one of the derivations of the Casimir effect uses virtual
particles for its derivation, some people consider the existence of
this effect as evidence for the existence of virtual particles.
But:
1. This is only evidence that the contribution of virtual particles
cannot be neglected in certain calculational schemes based on
virtual particles.
2. The effect from the virtual particles is infinite and hence
physically meaningless. Only through renormalization (which destroys
the naive interpration of virtual particles) can the finite,
measurable effect be obtained.
3. Well-understood phenomena such as the Coulomb interaction
would, by the same argument, olso have to be viewed as evidence
for virtual particles since, in some calculational schemes,
they arise by summing certain of the latter. But nobody seriously
interprets the Coulomb force as proof of virtual particles.
4. Most important: The Casimir effect can be understood and
calculated without the use of computational schemes employing
virtual particles. See:
R. L. Jaffe
The Casimir Effect and the Quantum Vacuum
http://lanl.arxiv.org/abs/hep-th/0503158
To conclude, the Casimir effect cannot be viewed as evidence for
the existence of virtual particles. As their name says, and as
explained in more detail elsewhere in this FAQ,
virtual particles do not exist (like real particles to whioch they
are contrasted in naming), in any meaningful sense of physical
existence.